The present invention relates to a camera, especially to a camera having two lens systems which can be switched over therebetween by means of a simple switching mechanism.
Lens-fitted photographic film packages are known which provide a kind of cheap throw-away camera. Such a lens-fitted photographic film package is adapted to focus on any subject in a range from about 1 m to infinity without the need for adjusting the focus of the taking lens. But such a lens-fitted photographic film package cannot focus on a subject nearer than 1 m, so that it cannot satisfy the requirement of close-up photography of flowers, characters on a document or the like.
Considering the above disadvantages, it has been suggested to provide a simple lens changeover mechanism wherein a single-element standard lens and a single-element macro lens are disposed side by side in a common lens holder which is rotatable in a plane perpendicular to the exposure light path, so that either one of these lenses can be used for photographing. This type of lens changeover mechanism is easy to operate and is simple in construction compared with conventional close-up lens systems wherein a supplementary lens is attached to a standard taking lens or the taking lens system itself is mechanically moved. In addition to the above advantages, because it can be manufactured at a low cost, this type of lens changeover mechanism is preferable to a lens-fitted photographic film package or other cheap cameras.
However, when manufacturing the above lens-changing mechanism, there would be the possibility of mispositioning the lenses in the common lens holder if the standard lens and the macro lens were not easily distinguishable, because both of these lenses are a single-element lens of a small diameter whose curvatures are not greatly different from each other.
Furthermore, although a single-element taking lens of the above-described conventional cheap camera is fitted into a recess of a corresponding diameter formed in a lens holder and is fixed thereto by a frame having an opening corresponding to the effective aperture of the lens, such a simple construction for holding the lens is not applicable to the above-described lens changeover mechanism because the lens holder should be rotatable in the camera housing.
As is known in the art, it is desirable in close-up photography to enlarge the depth of field because the focussing range of a macro lens is strictly limited. In order to enlarge the depth of field, it is preferable to stop down the aperture, but the possibility of underexposure is increased by this.